The present invention relates to Aerobic Bacterial Generators (ABGs) used for wastewater treatment and in particular an improved treatment method and unit that digests solids and expels highly treated liquid effluent.
Facultative Aerobic Bacterial Generators (FABGs) are devices described in Pat. No. 6,780,318 that are designed for the generation of a continuous supply of facultative bacteria within a conventional septic tank that can be used to digest clogging mucous compounds in the soil based disposal fields that septic tanks discharge to.
Such a device has several advantages for onsite wastewater treatment. One is that the units are portable and can be retrofitted into almost any size or type of existing onsite wastewater tank. Another is that the units are highly efficient, using pressurized air to generate a high volume stream of liquid over an internal matrix upon which the cultured bacteria grow.
Experience with these devices has shown that often their use results in creation of a high quality effluent, sometimes meeting what is referred to as “Secondary Treatment Standard”. This standard (NSF-40), by the National Sanitary Foundation is typically defined as having 30 mg/l or less of Biological Oxygen Demand (BOD) and 30 mg/l or less of Total Suspended Solids (TSS). Achieving such a standard is of great benefit since it allows a wider range of discharge options than a conventional septic leach system, the system wherein FABGs have typically been restricted to. Such options include direct aquatic discharge, discharge on lots typically too small for conventional septic leach, discharge into soils that are too tight for conventional septic based leach and systems where the ground water level is high and therefore to close to the discharge point for conventional septic effluent and finally use as irrigation water in reclamation systems.
Up until now the industry has utilized devices called Advanced Treatment Units (ATUs) to treat household waste to the secondary standard. Most of these are large scale mechanical units that include specialized tanks, mixers, stirrers, aerators, etc. to achieve treatment. It would be a great benefit to the industry if a simple and inexpensive, retrofittable, portable treatment unit could be developed that could not only meet secondary standards, but also do so in a range containment vessels including tanks of various sizes and shapes, ponds or other impoundments.
The previously mentioned Facultative Aerobic Bacterial Generator, unfortunately, has characteristics that make it difficult to consistently meet secondary treatment standards. The most widespread protocol currently used in the industry to certify onsite treatment units capable of meeting secondary treatment levels is the NSF-40 standard developed by the National Sanitation Foundation. To date attempts to meet this goal with a conventional FABG, such as is described in U.S. Pat. No. 6,780,318 have been unsuccessful.
So far all of the ATU systems that have met this standard have consisted of aerobic treatment tanks or devices that are preceded by a clarification tank that is equivalent to a septic tank. Typically only the soluble dissolved organic fraction is treated by these units. The bulk of the organic waste consists of particulate solids that settle out in the clarification tank and these must be pumped out on a regular basis and sent to a municipal treatment plant for final treatment.
The FABG is the only device in the onsite treatment field that is installed directly into tanks receiving both the soluble and particulate organic material. Experience with the devices has shown that almost all of the solids are degraded in the tanks This makes the FABG a far more useful tool than an ATU, in that almost all of the organic material is digested in situ rather than having to be shipped elsewhere for final treatment.
However, the fate of these solids is twofold. A substantial fraction is digested to CO2 but the remaining portion is processed into the bacterial population being generated within the device. Where FABGs are used to help clear clogged septic leach fields, as described in Pat. No. 6,780,318, these bacteria are not a problem. In fact they are necessary to the process. But bacteria will contribute to BOD as well as TSS and the effluent can be higher than the desired 30/30 BOD/TSS standard that would allow broader disposal options.
It is therefore a first object of the present invention to provide simple additional component that can easily be installed with a standard FBG to extend its treatment capacity so it can reliably produce effluent of secondary or better quality.
It is yet another object of the present unit to provide a waste treatment unit that digests organic material in situ, avoiding the need for the collection and disposal of sludge off site.